Poly(alkylene terephthalate) is used as a material for fibers, films, and molded articles, etc., due to excellent physical properties such as abrasion resistance, durability, and thermal stability, etc. Examples of the poly(alkylene terephthalate) include poly(ethylene terephthalate) (hereinafter, referred to as PET), poly(butylene terephthalate) (hereinafter, referred to as PBT), poly(1,4-cyclohexylenedimethylene terephthalate) (hereinafter, referred to as PCT), etc., that are commercially available. The most widely used material among them is PET, which is used for fiber, and bottle, etc.
The PET has a slow crystallization speed despite excellent physical properties thereof, and thus, when the PET is attempted to be used for engineering plastics requiring high crystallinity, a nucleating agent, a crystallization accelerator, etc., should be essentially used, and a mold temperature should be controlled due to a reduced production speed during an injection molding process.
On the other hand, the PBT has been widely used for the above-described engineering plastics since the crystallization speed of the PCT is faster than that of the PET. However, the PBT has a lower heat deflection temperature compared to the PET, and thus, the use thereof is limited for applications requiring a high degree of heat resistance despite excellent moldability as compared to the PET.
Accordingly, a method of improving moldability by adding various nucleating agents to a PCT resin having a high heat deflection temperature has been proposed to compensate for poor moldability and low heat deflection temperature of the PET and the PBT. Specifically, Patent Document 1 discloses a method of using an aliphatic polyester having a number average molecular weight of 8,000 or more as a nucleating agent to improve the crystallization speed of the PCT. Patent Document 2 discloses a poly(alkylene terephthalate) composition using an aromatic polyester as a nucleating agent. In addition, Patent Document 3 discloses a poly(alkylene terephthalate) composition including an oligomer polyester having a number average molecular weight of 4,000 or less.
However, Patent Documents 1 to 3 propose a composition for improving a crystallization speed of PCT by adding various nucleating agents to the PCT in a compounding step, and thus, the crystallization speed of the PCT itself is not improved. Therefore, it is necessary to provide a fundamental solution for improving the crystallization speed of the PCT itself.